The present invention relates to a lightweight, distributed load, high efficiency soundboard system for use with stringed musical instruments. More particularly, the present invention relates to improvements in bracing patterns and soundboard design for use on instruments such as the classical and steel string guitars, lute, mandolin, violin family instruments, piano, harpsichord and harp family instruments. In addition, the present invention relates to a stringed musical instrument of the guitar, violin and mandolin family having a removable and adjustable neck system including an adjustable sliding locking mechanism so that the height of strings relative to a fingerboard may be adjusted and to allow for tension balancing adjustments.
The improved soundboard bracing system is designed for use with traditional tone woods or man made materials. Advantageously, use of the improved soundboard bracing systems with traditional tonewoods provides unified long grain strength while overcoming inherent cross grain weakness. The disclosed invention provides a soundboard system that delivers excellent acoustic projection characteristics without undesirable free vibrational mode overtones. The soundboard system is most rigid where the transfer coupling for string tension loads are delivered and progressively less rigid to the outermost edges of the soundboard.
Even the earliest of stringed musical instruments used soundboards made of thin flat plates of lightweight quartersawn woods such as pine, spruce and cedar, with the grain of the wood running parallel to the strings for increased strength. The strings of these early instruments were attached to a small piece of wood called a bridge. Most often the bridge wood was selected of hardwood and glued to the top side of the soundboard, except in the cases of instruments where the strings were to be anchored to a tail piece or to the bottom end of the instrument. Where tail anchored or tail piece anchored strings were used the bridge was often not glued in place but held in place by the angled string pressure itself on the bridge, as is found in the violin family instruments, mandolins and arched top guitars of today.
The other end of the strings were attached to tuning pegs or other devices to tension the strings to the desired pitch. The tuning devices were to be found on the head of the instruments such as the lute, guitar, mandolin and violin at the opposite end of the neck from the body. The neck of the instrument was attached to the body of the instrument with the soundboard as its top. When the instruments were tuned, high forces were applied to the soft thin soundboard woods from the bridge due to string tension. Over time soundboard deformation often occurred. Also, force from the deformation could split or crack the wood usually parallel with the long grain.
Early instruments often used braces glued across the grain of the soundboard to strengthen the wood especially where experience indicated a likelihood of deformation or cracks. The size of the cross braces had to be selected carefully. If the braces were too small deformation could still occur. If the braces were too large, wave energy could be "stopped" or reflected away from the heavy brace having the effect of limiting the size of the active portion of the soundboard. A large instrument braced with braces that were too heavy could sound "small". Ancient stringed instruments with cross braced soundboards did not produce the volume and tone required in modern day instruments.
Over the centuries improvements to the art were made to make the instruments louder and more sonorous. During the period between 1550 and 1750, instruments of the violin family were improved and according to many authorities, perfected. These instruments employed a soundboard that was carved by hand into a vaulted arched shape where the load of the string tension was distributed over a wide surface area. In the case of the violin family, two other soundboard inventions were brought into play. The first was a bass bar which is a brace of wood running nearly parallel with the grain of the soundboard and located under the bass foot side of the bridge. The second was a sound post which is a rod of wood wedged between the soundboard and the back of the instrument very near the underside of the treble foot of the bridge. The bass bar was glued onto the soundboard with some pre-load, whereby the curve of the bass bar was greater than the curve of the inside surface of the soundboard so that when glued in place the soundboard is reinforced by a springing action. When properly fitted, the sound post not only aids in the support of the treble bridge foot but also serves to adjust the tonal quality of the instrument by its placement.
The soundboard inventions used in the violin family have worked extremely well with the large amounts of energy supplied by bowing excitation. However, when violin family strings are plucked by fingers the sounds produced do not sustain well.
As early as 1783, Josef Benedit of Cadiz, Spain was building guitars with thin flat soundboards 2 illustrated in FIG. 1 incorporating an invention called "fan bracing". These fan braces 4 were long thin pieces of wood with uniform thickness and height. Usually fan braces 4 were spaced closer together near the soundhole 10, gradually wider towards the bridge location 6 and even wider the braces 4 fan out behind the bridge 6. The volume and tone of such fan braced guitars was an improvement over crossed braced instruments. Fan bracing also provided better load distribution of string tension from the bridge 6 over the soundboard 2. By 1854, Antonio de Torres of Seville, Spain was building larger guitars with very thin soundboards braced with seven fan braces 4 and two stop braces 12 as also illustrated in FIG. 1. Two additional large stop braces 8 were added to isolate the active portion of the soundboard 2 from the soundhole 10. Guitars built today with bracing patterns as shown in FIG. 1 are called "Torres braced" after Antonio de Torres. Although the invention of nylon strings has changed the sounds produced from that of gut strings used in Torres' time, the modern classical guitar is basically the same instrument only somewhat improved since the 1850s.
Over years of string tension Torres style soundboards tend to crown up behind the bridge letting the bridge tilt forward so the guitar begins to play more and more out of tune while the strings begin to raise from the fingerboard until the guitar becomes too difficult to play. Fan braces act much like floor joists used in home construction. If joists or braces are placed closer together then the surface being braced is stronger. With Torres bracing, the fans are closer together near the soundhole so that the plate can be considered stronger in this area than where the braces fan out behind the bridge. However, in front of the bridge the Torres bracing pattern exhibits undesirable increasing resistance to flexing which has the effect of stopping wave energy and limiting the active portion of the soundboard. As the long braces gradually cross many of the long grains of the soundboard the normal cross grain weakness of the plate is somewhat overcome so that the soundboard acts more as a unified sound source than when no long grains are crossed. Some modern guitar makers use a bracing pattern that simply has several braces in parallel with the long grain of the plate. Although these simple parallel braces cause the strength of the plate to be equalized near the sound hole and behind the bridge, cross grain weakness has not been assisted. While some of the parallel braced guitars may seem loud to the player, most often Torres braced guitars will project better in a large room because of their more unified plate area sound source.
Between 1840-1850, Christian F. Martin of Nazareth, Pa. and others were building gut string guitars with what is now call "X-braced" soundboards as illustrated in FIG. 2. These guitars were primarily parlor guitars. The X-bracing 12 provided a strong soundboard 14 with more resistance to the crowning up problems associated with the ancient simple cross braced soundboards. It was not until the 1920s that the X-bracing pattern soundboards 14 were beginning to be used with steel strings. In 1929, the Martin Co. introduced a new OM (orchestra Model) guitar with steel strings on a X-braced soundboard with the neck of the guitar mounted at the 14th fret at the body instead of the traditional 12th fret mounting. In 1931, the Martin Co. introduced a large body 14th fret mounted X-braced steel string guitar called the D model or Dreadnought. FIG. 2 shows the most common bracing pattern used today on the modern steel string guitar soundboard 14. Very little has been changed from the 1930s. The steel string guitars of today have mostly large bodies with 14th fret mounted necks. Nearly all steel string guitars of today use two large crossed braces 12 with a single sound hole stop brace 16 located adjacent soundhole 17. One or two diagonal braces 18 are commonly used to limit the active portion of the soundboard 14 so that the larger portion of active surface is available to the bass side and the smaller to the treble. A bridge reinforcement plate 20 is glued to the underside of the soundboard directly below the bridge 22 glued to the top side of the soundboard 14. The remaining small braces strengthen the soundboard where cracking might otherwise occur. The X-braces 12 are usually built heavy enough to be considered stop braces during normal playing. Some makers build the braces 12 just light enough to allow movement during hard playing. The most active portion of the soundboard in the modern steel string guitar is the area behind the bridge 22 and bridge reinforcement plate 20 extending to the stop braces 18. While this is the most active area it is also the most likely area to crown up and deform. When deformation happens in the active area the bridge 22 begins to tilt forward so that the guitar begins to play more and more out of tune while the strings begin to raise from the fingerboard until the guitar becomes too difficult to play.
During the 1890s, Orville Gibson of Kalamazoo, Mich. was building carved arched top guitars and mandolins designed for steel strings. Through the years many attempts have been made to produce carved soundboards for plucked string instruments with some success mostly on instruments with steel strings where a pick or plectrum is used. Examples include the carved arch top mandolin and guitars of the early 1900s through the 1930s. While arch top instruments are being built today, most makers seek to build instruments with the qualities associated with arch tops built before World War II. Essentially, two bass bars are installed on most arch top instruments, one on the bass side as in the violin family and the other on the treble side near the other bridge foot. Typically the bridge on these instruments is held in place by the downward string pressure method and not glued to the soundboard. These instruments are not very loud when played with fingers alone. For this reason these arch top instruments have not been the instruments of choice where finger style playing is desired without the aid of electronic amplification. one of the best features of these carved top instruments is their stability after years of string pressure. The arch carved into the soundboards helps to the distribute the string pressure more evenly. Less distortion and deformation occurs in these instruments compared to flat top instruments. However, the soundboards of these instruments have to be almost twice as thick as those of flat braced soundboards. This accounts for most of the reason that the carved top instruments do not respond as well to the fingers alone.
One object of the present invention is to provide an improved bracing system to permit the soundboard to be as thin as possible, thereby improving tonal character. Advantageously, the bridge size can also be reduced.
The present invention for a distributed load guitar soundboard is suitable for both classical (nylon string) and steel string guitars. Unlike the previous examples shown in FIG. 1 for the modern classical guitar and FIG. 2 for the modern steel string guitar, the distributed load soundboard system of the present invention can be constructed with fundamentally identical bracing patterns. Both guitar types are tuned to the same frequencies. The notes on both instruments are alike. Only a small increase in the size of the active braces will be required to resist the extra tension of the steel strings. Additionally the modern steel string double strung or twelve string guitar has higher string tension than the steel string six string guitar. The active braces simply are increased in size again to balance the higher string tension and the distributed load guitar soundboard works equally well for the tension of twelve strings.
The distributed load soundboard system of the present invention can be constructed of traditional tonewoods or from man made materials such as carbon graphite, expanded polystyrene plastic rigid foam or other molded plastics, polyurethane or epoxy material compounds (mineral loaded or not) or even light weight metals. Different materials will have trade-offs not normally associated with the traditional tonewoods. It may not be possible to match the rich woody sounds of a spruce or cedar soundboard with a soundboard made from expanded polystyrene foam but a guitar made of plastic could be played in the rain or even underwater if desired. A wooden soundboard may be destroyed if it is emersed in water. Also as it becomes more and more difficult to obtain the quality tonewoods that were available even 10 or 20 years ago, synthetic materials may be required to build the soundboards of the future. The distributed load soundboard of the present invention can be constructed with lesser grades of existing tonewoods and still obtain good results because of the bracing system's ability to unite a larger surface of the soundboard into active wave motion.
In the past, one of the most important arts of the luthier was to select soundboard material with extreme light weight and yet high strength. Many luthiers select material according to the traditional grain counting method. Usually guitars are built with bookmatched soundboards. Bookmatched simply means that the soundboard plate is actually made up of two pieces of wood that have been split apart by sawing and folded out so that the grain of one side is the mirror image of the other side. It is traditional to join the wood in the center of the soundboard with the close grain at the center and the grain at the outer sides gradually becoming farther apart. The center grains are often counted and graded by grains per inch with the more desirable tonewood having very close grains that are straight and gradually becoming wider to the edges. Just as with floor joists, if the grains at the center of the soundboard are closer then the board is stronger in the center. This is the reason for the grain counting method. The distributed load soundboard of the present invention can be constructed with tonewood that has wider grains than the traditional choices because the bracing itself is stronger in the center so that the tonewood plate could be made with wood that would currently not be selected. Wood that is somewhat uniform in grain width or has wider grain on the bass side and gradually becomes closer towards the treble side would work very well. In practice the soundboard plates of distributed load soundboards can be thinner than the plates of traditional soundboards. The natural resources (tonewood) can be better conserved if lesser grade woods are not wasted and if thinner wood is required.
Existing traditional bracing patterns developed for soundboards have evolved over time to produce different types of sounds. Each bracing pattern has some advantages. Generally a highly skilled luthier is able to produce instruments using these traditional patterns that is loud enough for studio or recital work. Only a few luthiers are able to produce instruments loud enough to cover a large concert hall. With the existing patterns trade-offs are inevitable even when using the best tonewoods. Often to get loud sonorous treble notes the bass frequencies are sacrificed. If the instrument is very loud to the musician it may not be loud to the audience as is the case often with bracing patterns that run truly parallel with the grain of the soundboard. Torres braced instruments and their modifications generally produce a somewhat more efficient acoustical coupling for larger rooms, however, it is also common for music played and heard near the musician at the front of a large room to become severely unbalanced when heard from the rear of the room.
The distributed load soundboard system provides for a larger surface area of the soundboard to be set into active wave motion while allowing the weight of the structure to be minimized so that soundwaves may be produced with greater efficiency. The present invention relates to improvements in bracing patterns so that balance of sound is maintained in very large halls or even out of doors.
A soundboard that is too stiff and does not allow movement will not produce sound as well as a soundboard that is allowed to move more freely. If the soundboard is too flexible, especially where the string tension is transferred to the soundboard at the bridge, deformation to the soundboard will be the result. Also a soundboard that is too thin or uncontrolled by the braces can develop undesirable free vibrational modes or overtones. The optimum condition is where the soundboard is made rigid at the bridge and becomes progressively less rigid away from the bridge in all directions so that the soundboard will move freely when excited by string vibrations but resist deformation from string tension in exact balance.
According to one aspect of the invention, a soundboard apparatus for a stringed musical instrument is provided. The apparatus includes a soundboard having first and second side surfaces, a bridge coupled to the first side surface of the soundboard for securing a plurality of strings to the soundboard, and a plurality of braces coupled to the second side surface of the soundboard. The plurality of braces are configured to intersect at a point located directly below the center of the bridge to strengthen the soundboard adjacent the bridge. In the illustrated embodiment, the plurality of braces are mirror symmetrical about an axis of symmetry extending through the bridge.
In one illustrated embodiment, the plurality of braces are catenary braces having a generally flat side surface and a curved catenary side surface. The generally flat side surfaces of the plurality of catenary braces may be coupled to the second surface of the soundboard, or alternatively, the curved catenary side surfaces of the plurality of catenary braces may be coupled to the second surface of the soundboard.
According to another aspect of the present invention, an adjustable locking apparatus is provided for securing a neck to a body of a stringed musical instrument. The apparatus includes a first track member located on the neck, and a second track member located on the body. The second track member is formed to slidably engage the first track member to align the neck in a selected position relative to the body. The apparatus also includes a fastener for holding the first and second track members in the selected position to secure the neck relative to the body.
In the illustrative embodiment, the first track member includes a male dovetail coupled to the neck and the second track member includes a mount block coupled to the body. The mount block is formed to include a female dovetail groove for slidably receiving the male dovetail. Also illustratively, the fastener includes at least one bolt extending through the mount block and engaging a threaded insert in the male dovetail to secure the male dovetail relative to the mount block. A relief slot is formed in the mount block adjacent the female dovetail groove. A clamping bolt is also provided for engaging the mount block to adjust a clamping force applied by the dovetail groove against the male dovetail.
In the illustrated embodiment, the mount block is formed to include at least one elongated slot. Each elongated slot is configured to receive a fastener therethrough. Each fastener is configured to engage a threaded insert in the male dovetail to secure the mount block relative to the male dovetail. Each fastener is slidable in the at least one elongated slot to permit adjustment of the position of the neck relative to the body.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of the preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.